Hand-controlled grinding tood, for machining round objects

ABSTRACT

In a power grinder ( 1 ) with a motor ( 6 ) and a gear ( 7 ) that drive an oscillating drive means ( 2 ), which moves a grinding belt ( 3 ) secured to it to reciprocate, a simple change of the grinding belt ( 3 ) is made possible by providing that the grinding belt ( 3 ) has a hook-and-loop closure ( 4 ), or the grinding belt ( 3 ) is disposed with its first end ( 11 ) on the drive means ( 2 ), and its second end ( 12 ) is connected to a handle ( 13 ).

PRIOR ART

[0001] The invention is based on a power grinder, having a motor and agear that drive an oscillating drive means about a deflection angle; thedrive means drives a grinding belt, secured to it, to reciprocate.

[0002] For machining round objects in the built-in state, it isnecessary for the grinding belt to adapt to the radius of that object.Moreover, there must be a possibility of releasing or closing thegrinding belt. This is attained, by the devices available on the market,by means of an endless grinding belt. If built-in objects are to beground, the grinding belt must be severed and then glued together againafterward. This is very complicated and expensive.

[0003] From German Patent Disclosure DE 34 47 828 A1, a motor-drivablegrinding apparatus is also known, which is used for grinding, smoothingand polishing of preferably round bars and tubes. It uses an opengrinding belt, wrapped in a loop around the workpiece, that is held byits two ends in two clamping or tensioning devices of the grindingapparatus. Via a movement device, a gear that can be driven by motor ina rotary motion in the same direction sets the two clamping andtensioning devices and thus also the grinding belt into an alternating,synchronized opposed motion, which pulls the grinding belt over theworkpiece. Thus the grinding action is attained. Although such anoscillating motion enables high operating safety and good manipulationof the grinding apparatus, nevertheless the effort and expense forchanging the grinding means is very high, since the grinding belt has tobe removed with its ends from the clamping or tensioning device, and thenew grinding belt has to be inserted back into this device.

[0004] Advantages of the Invention

[0005] A power grinder according to the invention as defined by thecharacteristics of claim 1 or claim 8 has the advantage over the priorart that a simple change of the grinding belt is possible. By means ofthe closure according to the invention on the grinding belt as definedby claim 1, it is unnecessary to perform complicated cutting apart andgluing of the grinding belt, or releasing and securing the ends from andto a clamping or tensioning device. The release and securing of thegrinding belt is done for instance in the case of a hook-and-loopclosure by simple pressing actions, without requiring additional steps.Moreover, the hook-and-loop closure offers adequately high securityagainst an unintended release.

[0006] It is advantageous if the closure is in engagement with the drivemeans. To that end, in the case of a hook-and-loop closure, forinstance, the grinding belt is first wrapped around the object to bemachined and is then pressed with its two ends against the drive means;the counterparts of the hook-and-loop closure of the grinding belt aredisposed on the drive means. Another option is to guide the grindingbelt, once it has been wrapped around the object to be machined, all theway around the entire drive means and to join the two ends of thegrinding belt directly to one another, between the drive means and theobject to be machined, by means of a hook-and-loop closure.

[0007] It is especially advantageous if the drive means is a swing head,which in particular takes the form of a wheel. As a result, it ispossible in a simple way to wrap the grinding belt around the swing headand secure it to the swing head, or to connect its two ends together,between the swing head and the workpiece to be machined, as describedabove.

[0008] It is also advantageous if the face end of the gear, on its sideremote from the motor, has a beveled drive shaft on which a peg that isin engagement with the drive means is disposed eccentrically. As aresult, the driving motion, as a rule rotation, that is imparted by thegear is converted into an oscillating motion. This is done in a way thatis very simple to achieve and is not very complicated structurally. Itis especially preferred if the peg is seated in a sliding block guide onthe drive means.

[0009] It is also preferred if the closure is embodied on the first endand on the second end of the grinding belt. Compared to being disposedinside the grinding belt, the entire length of the grinding belt canthus be utilized. This contributes to making it possible for roundobjects with quite different diameters to be machined with the samegrinding belt.

[0010] Another feature according to the invention provides that thegrinding belt is disposed with its first end on the drive means and itssecond end is connected to a handle. Once again, this makes simplechanging of the grinding belt possible. It is also thereby especiallysimply possible to wrap the grinding belt around the object to machined,since the grinding belt does not have to be released from its fasteningpoints at all.

[0011] It is advantageous if an elastic element, is disposed between thesecond end of the grinding belt and the handle. As a result, theoscillating motion of the grinding belt is not transmitted in full tothe handle and hence to the hand of the user.

[0012] It is also advantageous if the first end of the grinding belt ismounted rotatably on the drive means. As a result, in places that arehard to reach but need to be machined, this makes it possible for theuser not to have to assume unnatural hand and arm positions.

[0013] It is also advantageous if the drive means is a machine insert.As a result, the grinder is universally usable, since still otherinserts besides the grinding belt can be coupled to the machine insert.

[0014] Further advantageous features of the invention are the subject ofthe dependent claims.

DRAWINGS

[0015] Exemplary embodiments of the invention are described in furtherdetail in the ensuing description in conjunction with the associateddrawing.

[0016] Shown are:

[0017]FIG. 1, a first exemplary embodiment of a power grinder with ahook-and-loop closure;

[0018]FIG. 2, a section through a second exemplary embodiment of agrinder with a grinding belt with a hook-and-loop closure;

[0019]FIG. 3, a schematic detail of FIG. 2 without the grinding belt;and

[0020]FIG. 4, a third exemplary embodiment of a grinder, with a handleat the end of the grinding belt.

[0021] In FIG. 1, a power grinder 1 is shown, which has a drive means 2in the form of a swing head 5. The drive of the swing head 5 isaccomplished by the means described in FIGS. 2 and 3 for a furtherexemplary embodiment. The swing head 5 is set into an oscillatingmotion. In the process, it oscillates about a shaft 16. A grinding belt3 is wrapped around the swing head 5. The grinding belt 3 has a closure4, by which the first end 11 is releasably connected to the second end12 of the grinding belt 3 to form a ring. Below a hook-and-loop closure4 will be described as an example of the closure 4. The hook-and-loopclosure 4 is disposed such that it is located between the swing head 5and an object 17 (FIG. 2) to be machined. This assures very simplechanging of the grinding belt 3. All that is necessary is to release thetwo ends 11, 12, which are in engagement with one another by means ofthe hook-and-loop closure 4, from another. Moreover, in this exemplaryembodiment, once the grinding face of the grinding belt 3, shown on theinside thereof, has become worn down in the region of the object 17 tobe machined, this face can be rotated, such that an unused piece of thegrinding belt 3 is in contact with the object 17 to be machined. As aresult, the grinding belt 3 can be used for longer, thus saving moneyfor the user. To put the power grinder 1 into its machining position,the hook-and-loop closure 4 of the grinding belt 3 is opened. Next, thegrinding belt 3 is wrapped around the object to be machined, and thehook-and-loop closure 4 is closed again. With such a grinder 1, the usercan instantly begin machining the object 17. Changing a worn grindingbelt 3 is equally fast.

[0022] In FIGS. 2 and 3, a second exemplary embodiment of a powergrinder 1 of the invention is shown. In principle, this second exemplaryembodiment functions like the first exemplary embodiment shown inFIG. 1. Identical parts, or those functioning the same way, areidentified by the same reference numerals. Below, only the distinctionsfrom the first exemplary embodiment described above will be addressed.

[0023] The swing head 5 is moved by a gear 7, which is supported in ahousing 18 of the grinder 1 and is driven by a motor 6. The drive is notessential to the invention, and so these elements will not be describedin further detail here. A drive shaft 8, which rotates about alongitudinal axis A of the grinder 1, is embodied on the end of the gear7. The rotation of the drive shaft 8 is converted into an oscillatingmotion about a deflection angle D along the double-headed arrow C bymeans of a peg 9, disposed eccentrically on the drive shaft, thatengages a sliding block guide 10 on the swing head 5. This conversion isaccomplished by disposing the peg 9 eccentrically to the longitudinalaxis A along a peg axis B. Further detail of this embodiment is shown inFIG. 3. On the face end, the drive shaft 8 is defined by a terminationarea 20 that is tilted relative to the longitudinal axis A. The peg 9 isdisposed on this termination area 20, eccentrically to the longitudinalaxis A. The peg axis B formed by the peg 9 extends in its extensionthrough the shaft 16 about which the swing head 5 oscillates. Thedeflection angle D is defined by the spacing between the peg axis B andthe longitudinal axis A along the termination area 20. The value of thedeflection angle D corresponds to the amplitude that is attained in theoscillation of the swing head 5 about the shaft 16 along thedouble-headed arrow C (FIG. 2). The peg 9 is supported rotatably in thesliding block guide 10 by means of a bearing 19. In FIG. 3, for the sakeof clarity, the grinding belt 3 has not been shown.

[0024] The fundamental distinction between this second exemplaryembodiment and the first exemplary embodiment shown in FIG. 1 has to dowith securing the grinding belt 3. It can be seen from FIG. 2 that boththe first end 11 and the second end 12 of the grinding belt 3 are fixed,each by means of a hook-and-loop closure 4, to the swing head 5. Formachining the object 17, the grinding belt 3 is detached from the swinghead 5 on its first end 11 and/or second end 12, wrapped around theobject 17, and then fixed to the swing head 5 again by means of thehook-and-loop closures 4. This assures fast starting of the grinder 1and equally fast replacement of the grinding belt 3. The grinding region21 on the object 17 is the region that is remote from the grinder 1. Thegrinding belt 3 is moved back and forth over the grinding region 21 bythe oscillating motion of the swing head 5, as a result of which thesurface of the object 17 is ground down in the grinding region 21.

[0025] In FIG. 4, a third exemplary embodiment of a power grinder 1 ofthe invention is shown. Once again, parts that are identical or functionidentically are identified by the same reference numerals. The first end11 of the grinding belt 3 is mounted rotatably on the drive means 2. Thedrive means 2 is embodied on a machine insert 15. A handle 13 is mountedon the second end 12 of the grinding belt 3, via an elastic element 14.A spring 14 will be described below as the elastic element 14. Arbitraryother elastic elements 14 can be used equally well. To enable machiningan object 17 (not shown) with such a grinder 1, the handle 13 is wrappedaround the object 17, so that the grinding belt 3 rests on the grindingregion 21 (not shown) under the tension of the spring 14. A grindingmotion takes place in the grinding region 21, as just described above,as a result of the oscillating motion of the drive means 2. By means ofthe spring 14, the oscillating motion, which is executed by the grindingbelt 3 and transmitted to the handle 13, is reduced sharply, so that theuser can hold the handle 13 without problems.

[0026] An advantage of this exemplary embodiment is that the grindingbelt 3 need not be released from the grinder 1. Fast machining of theobject 17 is thus assured. It is moreover possible to use the grindingbelt 3 over a wide range of its length, depending on the region in whichthe grinding belt 3 is placed, by means of the handle 13, around theobject 17. As a result, the grinding belt 3 can be used longer withouthaving to be replaced. This saves money for the user. This effect isfurther enhanced if the grinding belt 3 is embodied as a terminationarea on both sides. Because of the rotatable support of the first end 11on the drive means 2, the face of the grinding belt 3 that pointsoutward in FIG. 4 can thus also be used for grinding round objects 17.The capability of rotating the grinding belt 3 relative to the drivemeans 2 offers the further advantage that the user need not assumeunnatural hand and arm positions at poorly accessible places on anobject 17 to be ground. This enhances the ease of use of the deviceenormously.

[0027] For all three exemplary embodiments, the following items can forinstance be used as the grinding belt 3:

[0028] A grinding cloth belt, grinding nonwoven, polishing belt, sawwire, bristle belt, or etching belt.

[0029] In addition to the use of a hook-and-loop closure 4 on thegrinding belt 3, it is equally possible to use push buttons, clamps,screws, hooks, or similar connecting means.

[0030] The result is a very broad range of use. With a grinder 1according to the invention, the following objects can for instance bemachined:

[0031] A landing, especially a landing on a staircase; a yard fence ofround or half-round profile; table and chair legs turned on a lathe;water lines, heating pipes, downspouts for roof gutters; posts;streetlights; traffic lights; and frames for bicycles and motorcycles.

[0032] The following machining operations can furthermore be performed:rounding off edges of furniture, machining small parts using stationarygrinding and polishing devices, etching, removing adhesive residues,sawing circular cutouts, and sawing pipes using saw wire. List ofReference Numerals 1 Power grinder 2 Drive means 3 Grinding belt 4Closure, in particular hook-and-loop closure 5 Swing head 6 Motor 7 Gear8 Drive shaft 9 Peg 10 Sliding block guide 11 First end 12 Second end 13Handle 14 Elastic element, in particular spring 15 Machine insert 16Shaft 17 Object 18 Housing 19 Bearing 20 Termination area 21 Grindingregion A Longitudinal axis B Peg axis C Double-headed arrow D Deflectionangle

1. A power grinder (1), having a motor (6) and a gear (7), which drivean oscillating drive means (2) about a deflection angle (D), which drivemeans drives a grinding belt (3), secured to it, to reciprocate,characterized in that the grinding belt (3) is detachably connectable toa ring by means of a closure (4), in particular by means of ahook-and-loop closure.
 2. The grinder (1) of claim 1, characterized inthat the closure (4) is in engagement with the drive means (2).
 3. Thegrinder (1) of claim 1 or 2, characterized in that the drive means (2)is a swing head (5), which in particular takes the form of a wheel. 4.The grinder (1) of one of the foregoing claims, characterized in thatthe gear (7), on its side remote from the motor (6), has a drive shaft(8) on its face end, on which shaft a peg (9), which is in engagementwith the drive means (2), is disposed eccentrically.
 5. The grinder (1)of claim 4, characterized in that the eccentric peg (9) is disposed atan angle to the drive shaft (8) that is equal in size to the deflectionangle (D) of the drive means (2).
 6. The grinder (1) of claim 4 or 5,characterized in that the peg (9) is seated in a sliding block guide(10) on the drive means (2).
 7. The grinder (1) of one of the foregoingclaims, characterized in that the closure (4) is embodied on the firstend (11) and on the second end (12) of the grinding belt (3).
 8. A powergrinder (1), having a motor (6) and a gear (7), which drive anoscillating drive means (2) about a deflection angle (D), which drivemeans drives a grinding belt (3), secured to it, to reciprocate,characterized in that the grinding belt (3) is disposed with its firstend (11) on the drive means (2) and its second end (12) is connected toa handle (13).
 9. The grinder (1) of claim 7, characterized in that anelastic element (14), in particular a spring, is disposed between thesecond end (12) of the grinding belt (3) and the handle (13).
 10. Thegrinder (1) of one of claims 7 or 8, characterized in that the first end(11) of the grinding belt (3) is mounted rotatably on the drive means(2).
 11. The grinder (1) of one of the foregoing claims, characterizedin that the drive means (2) is a machine insert (15).